As you are not using any Oracle software so far, technically you should open this in a MySQL forum. However, to follow up -

1. Have you checked the obvious ? Does the ODBC driver exist in the directory -

/opt/oradb/patches/myodbc-5.3.4/lib/libmyodbc5.so

2. Did you set any ENV variables before running ISQL ? At a minimum you should set the LD_LIBRARY_PATH to include the path to the driver lib directory, and set the ODBCINI variable to the location of the odbc.ini file.

I dont have driver "libmyodbc5.so" in the indicated location i.e "/opt/oradb/patches/mysql connector/lib". i just downloaded mysql connector odbc 5.3.4 and unzip it ,that's it .How can i install this driver, do i need to run "mysql installer" located in "/opt/oradb/patches/mysql connector/bin"? can you help please,because first time i m doing this so i dont know ?